For coupling a string member such as a belt in various applications such as clothes, bags, shoes and packages, there has been typically used a buckle whose plug and socket are detachably connected to each other.
Such a buckle should be easy to handle for connection and separation of the plug and the socket and should be prevented from unintentional and accidental separation of the plug and the socket. As a product responding to such needs, a side release buckle including a lateral pair of lock arms has been used.
A typical side release buckle includes a plug and a socket, each of which is provided with a belt attachment (see Patent Literature 1 and Patent Literature 2).
The plug includes: a plug base including the belt attachment; and a lateral pair of legs (lock arms) disposed on a socket-opposed side of the plug body. The socket includes a hollow cylindrical socket body. The socket body has a housing space (cavity) into which the plug is inserted from a plug-opposed side of the socket body. Engaged portions being engageable with engaging portions of the legs are formed in the housing space. Thus, when the plug is brought adjacent to the socket and the legs are inserted into the housing space, the plug is engaged with the socket. The socket body has openings formed on the lateral sides thereof. The openings communicate with the housing space, so that the pair of legs are projected from the openings. When the legs projected from the openings are held by hand and deformed to approach each other, the plug and the socket can be disengaged from each other.
When such a side release buckle is held by hand, the legs are accidentally pushed and thus the plug and the socket are unintentionally disengaged from each other. Accordingly, in order to avoid such unintentional disengagement, a double lock side release buckle has been provided.
A buckle disclosed in Patent Literature 1 is a double lock side release buckle including: a side release lock mechanism provided by a lateral pair of legs (first and second legs); and a so-called front push lock mechanism provided by a third leg formed between the lateral pair of legs.
For disengaging the plug and the socket of such a side release buckle from each other, the legs on lateral sides of the buckle are pushed inward for disabling the side release lock mechanism while a release button on a top side of the buckle is pushed for disabling the front push lock mechanism.
Thus, even when the buckle is held and the lateral pair of legs are accidentally pushed, lock can be maintained, so that unintentional disengagement between the plug and the socket can be prevented.
A buckle disclosed in Patent Literature 2 includes: a side release lock mechanism provided by a lateral pair of legs; and a movable lock member disposed on a top side of the socket. A projection of the lock member is brought into contact with the legs in the socket to prevent disengagement of the legs.
In such a side release buckle, as long as the lock member is set at a double lock position, even when the buckle is held and the lateral pair of legs are accidentally pushed, lock can be maintained because the lock member prevents the movement of the legs. Thus, unintentional disengagement between the plug and the socket can be prevented. On the other hand, when the lock member is moved from the double lock position to a release position, the lock member is not in contact with the legs, so that the double lock function is disabled and thus the plug and the socket can be engaged and disengaged in the same manner as those of a typical side release buckle.